The present invention relates to a semiconductor integrated circuit and an optical disk device having the same and, more particularly, to a technique effective to achieve higher precision and lower consumption power by reducing a semiconductor chip occupation area.
An optical disk is diversified to a CD (Compact Disk), a DVD (Digital Versatile Disk), a BD (Blue-Ray Disk), and the like, and the system configuration of an optical disk drive for recording/reproducing an optical disk is complicated. A semiconductor integrated circuit mounted on an optical disk device is requested to achieve lower cost and lower power consumption and, on the other hand, has to record/reproduce data to/from the diversified disks.
A semiconductor integrated circuit mounted on an optical disk drive has therein a servo error signal generating circuit for generating a servo error signal of tracking servo and focus servo from an electric signal output from an optical disk pickup light receiving element and a wobble signal generating circuit for generating a wobble signal used at timings of physical address information on an optical disk, disk rotation control, and recording data from the electric signal.
In the case of reproducing information on an optical disk, it is necessary to control track servo (tracking servo) for making an optical beam emitted from a semiconductor laser light emitting device follow a predetermined track in an optical disk, focus servo for making a focal point match on the recording face of the optical disk, speed servo for controlling the rotational speed of the optical disk, and the like.
For the tracking error signal, two kinds of methods exist. The first method is a differential phase detection (DPD) method for reproduction recommended in the standards of BD-ROM and DVD-ROM, and the second one is a differential push-pull (DPP) method used for recording in an optical disk device and reproduction of a disk such as a CD-ROM. Particularly, the differential phase detection (DPD) method is a detection method recommended in the standards of disks in which reproduction data is already written and to which data cannot be recorded such as a BD-ROM and a DVD-ROM. The method performs detection on the basis of high-frequency reproduction data on a disk, so that the semiconductor integrated circuit is required to perform high-speed signal process.
The following patent document 1 discloses a DPD signal generating apparatus using output signals of four regions A, B, C, and D of a light receiving element divided by the track direction axis and the orthogonal axis direction of an optical disk. A first phase comparator detects the phase difference between a binary signal of the region A and a binary signal of the region B, and a second phase comparator detects the phase difference between a binary signal of the region C and a binary signal of the region D. A detection result of the first phase comparator and a detection result of the second phase comparator are added by an addition circuit, and an addition result is supplied to a servo controller via a low-pass filter.
The following patent document 2 discloses a tracking error detection circuit by the DPD method using output signals of four divided regions A, B, C, and D of a light receiving element of an optical disk. A signal from the region A and a signal from the region C are added by a first addition circuit, and a signal from the region B and a signal from the region D are added by a second addition circuit. The first addition output signal of the first adding circuit and the second addition output signal of the second adding circuit are supplied to a first level comparator circuit and a second level comparator circuit via a first equalizer circuit and a second equalizer circuit, respectively. A first binary signal of the first level comparator circuit and a second binary signal of the second level comparator circuit are supplied to a phase comparing circuit. First and second comparison output signals of the phase comparing circuit are supplied to a subtraction circuit via first and second low-pass filters, respectively, and a tracking error signal is generated from an output of the subtraction circuit.
On the other hand, in the CD-R (Recordable), CD-RW (Rewritable), DVD-R, DVD-RW, DVD-RAM, BD-R1, BD-RE, and the like as recordable optical disks, a format for wobbling a track in order to accurately detect linear velocity in each of radius positions is employed. By detecting a wobble signal of a track, detection of physical address of the optical disk, rotation control of the optical disk, recording data timing control, and the like can be performed.
The following patent document 3 discloses a wobble signal extracting circuit using output signals of the four regions A, B, C, and D of a light receiving element. A first variable gain amplifying circuit adds signals of regions A and D to generate a first arithmetic result A+D, and a second variable gain amplifying circuit adds signals of regions B and C to generate a second arithmetic result B+C. The first arithmetic result A+D and the second arithmetic result B+C are supplied to the subtraction circuit via a first automatic gain control circuit and a second automatic gain control circuit, respectively. The subtraction circuit generates a wobble signal W by executing the arithmetic operation (A+D)−(B+C).
The following patent document 4 discloses a wobble detecting circuit for executing the analog arithmetic operation of (A+D)−(B+C) described in the patent document 3 by digital arithmetic process. Two analog addition signals are supplied to two high-speed sampling circuits via two binarizing circuits, a digital subtraction signal of the high-speed sampling circuits is supplied to a digital filter, and the digital wobble signal is supplied to a digital wobble detector.